Process of making a fertilizer



' phate may Patented June 13, 1933 UNITED s r JOHN n. cmornnns, or lmms'roiv, ALABAMA, ASSIGNOR TO swam:

A oonronA'rIoN or ALABA A noonronmrnn,

TESV AT NT OFFICE- assume,

J PROCESS OF MAKING A. FERTILIZER No Drawing.

This invention relates to a process of making a fertilizenand in particular to a process of treating calcium superphosphate, or equiv' alent compounds. i

The object of this invention is to provide the more eflicient utilization of a process for the sulphuric acid which superphosphate.

A further object of this invention is to provide a process by which dicalcium phosphate and ammonium salts may be economically repared.

A still further object is to provide'a process 7 for" economically utilizing ammonium carbonate in solution, or when present, 1n by-.

product gases as mixtures of ammonia and carbon dioxide,-such as are obtained during the synthesis of urea'from ammonia and carbondioxide. v I i 4 The product produced by my process may be used directly as a fertilizer or as an in-' gredient of mixed fertilizers. It may be separated into two parts by leaching with Water so as to give aninsol'uble constituent consisting of calcium carbonate and dicalcium phos phate and a soluble portion consisting of ammonium sulphate and diammonium phosphate.

t is already well known that superphosmixture of dicalcium phosphate, ammonium sulphate and calcium sulphate obtained. This reaction may be written:

Superphosphate also sometimes known as acid phosphate is made by treating bone phosphate of lime or phosphate rock with sulphuric acid. monocalcium phosphate and calcium sulphate 'intlie proportions of one molecular weight of the former to two molecular weights of the latter. l I

I have foundthat reaction 1 above may be carried out more eil'ectively, and with a greater utilization of. the sulphuric acid by the addition of carbonic acid. Carbonic acid or Application filed April 21,

is ordinarily used in treating phosphate rock when producing J without causing reversion of the available betreatedwith ammonia and a acid phosphate which contains the above asman It consists essentially of 1930. Serial No. 446,193.

even carbon dioxide gas may be used, the latter being combined with the ammonia'entering into the reaction. I have found that in operating in my preferred manner I cause less reversion to take place than when the re action is carried out in the usual way.

In operating my improved process one thus obtains a greater utilization of ammonia phosphate to take place. By reversion is meant the productionduring treatment or afterwards of phosphates which are neither water soluble nor ammonium citrate soluble. The products obtained by my process are mixtures of dicalcium phosphate and calcium. carbonate, insoluble in water, and ammonium sulphate and diammonium phosphate, the latter two substances being water soluble. A

\ desired.

separation may be made in the usual way if g phosphate and calcium sulphate inthe pro- .portion of one molecular weight of the former to two molecular weights-of the latter and treat them with a solution of ammonium carbonate at ordinary or slightly elevated w The solution preferably con-' tains about 2.5 gram formula weights of am-. monium carbonate per liter of water. In place of a mixture of monoc'alciunrphosphate and calcium sulphate, I may employ the mixture ordinarily known as super-phosphate or temperatures.

substances in the proper proportion. The re-j action which takesplace may be written:

2- C3. 2 .H2O a S O4 -2H2O The aqueous mixture which is obtained as above may nowbe dried at a low temperature to give a mixture of dicalcium phosphate, calcium carbonate, ammonium sulphate and diammonium phosphate. The product thus obtained may serve as \a fertilizer. By drying at a higher temperature, it is possible to convert the diammonium phosphate into monoammonium phosphate and ammonia,'

I no

the latter being recovered and reused in the process.

Instead of using solutions of ammonium carbonate, the treatment may be carried out 5 as above, using ammonia water of the proper equivalent strength and carbon dioxide gas or gases containing carbon dioxide passed through the solutions, thus building up a carbonate concentration during treatment. The proportion of carbon dioxide to ammonia may be as indicated in the above reaction, or it may be present in a greater amount.

After treatment as above, the insoluble substances may be separated from the soluble salts in thereaction products by known means. The insoluble calcium carbonate anddicalcium phosphate may be used as a ferti- I lizer ingredient, or for various chemical purposes. The soluble salts may be recovered by drying or by evaporation and crystallization,

either as a mixture of ammonium sulphate and diam'monium phosphate, or after evaporation at a higher temperature as ammonium sulphate. and monoammonium phosphate. These substances are suitable as fertilizers or for other chemical purposes.

What I claim is: Process for producing a mixture of dicalcium phosphate and ammonium salts from a mixture of monocalcium phosphate and calcium sulfate comprising reacting'said monocalcium phosphate and calcium sulphate together with a solution containing six moles of ammonia and two moles of carbon dioxide for each molecule of P 0 to be reacted upon,

drying the resulting mixture at a tempera ture sufficiently high to convert the diammonium phosphate in the mixture to monoammonium phosphate, and recovering the 40 ammonia driven ofi' in drying for reuse in the said solution.

In testimony whereof I afiix my signature.

JOHN N OAROTHERS. 

